Electrical circuit breaker



Oct. 19, 1937. u. A. COMB] 2,096,608

ELECTRICAL cmcun' BREAKER Filed Juli 2a, 1936 2 Sheets-Sheet 1 mv moR M av 1%., #ATTQRNEY.

Oct. 19, 1937.

u. A. OMBI ELECTRICAL CIRCUIT BREAKER Filed July 28, 1936 2 Sheets-Sheet 2 ALATTORNEY.

Patented Oct. 19, 1937 UNITED STATES PATENT OFFICE Application July 28, 1938, Serial No. 92,97. In Great Britain July 18, 1935 Claims. (01. zoo-'11s) This invention relates to electrical circuit breakers and more particularly tocircuit breakers wherein the circuit is broken in response to a predetermined current overload.

One object of this invention is to provide circuit interrupting means of a simple, inexpensive and reliable character which, while possessing a desirable time lag on overloads within definite limits, is more critical to an overload of predeterl0 mined value than is usual with devicts of similar character hitherto known.

Another object of the invention is to provide a construction of circuit breaker which is adapted for use with advantage as a substitute for wire fuse devices in commercial and domestic electrical installations, thus saving time and trouble in re-establishi'ng an electrical circuit which has been interrupted owing to overload.

A further object of this invention is to provide a relatively cheap electrical circuit breaker device which cannot easily be tampered with, nor be rendered inoperative by the user inadvertently during operation, nor be rendered inoperative owing to long periods of inaction.

:5 A still further object of this invention is to provide circuit breaking means capable of limiting consumption in a safe, reliable and practical manner. v

In order that the nature of the present invention may be better understood one embodiment shown by way of example in the accompanying drawings will be described hereinafter from which further objects of the invention will be apparent. In the drawings:-

Fig. 1 is a front elevation of a thermally controlled form of the improved circuit breaker with its cover removed.

Pig. 2 is a fragmentary view showing a simple modification of a detail.-

Fig. 3 is a front elevation of the device of Fig. 1

with all the parts enclosed by a cover which can be sealed in place;

Figs. 4, 5 and 6 are fragmentary views showing progressive stages of operation of the toggle mechanism;

Fig. 7 is a detail view of one of the toggle elements drawn to an enlarged scale;-

Figs. 8, 9, 10 and 11 arefragmentary rear views,

showing progressive stages of operation of the contacts while the mechanism is being "set";

Fig. 12 is a detail rear perspective view of the compound contact blade showing the parts relatively displaced to facilitate description.-

s5 Figs. 13 and 14 are detail views showing the application of a luminous signal to the improved circuit breaker.

In the form of circuit breaker shown in the accompanying drawings the parts are mounted on a base II of insulating material and enclosed 5 by a cover II, also of insulating material. A rotatable operating knob I! for the device is suitably in the form of an indicator II, which proiects through an aperture II in said cover and which is operable manually between positions ini0 dicated by "on" and oil, respectively.

Mounted on the base II are stationary terminals I), II which are connected with the conductors of the circuit to be controlled. Terminal II is in the form of a contact, as hereinafter de- 15 scribed.

Co-operating with the two terminals II, II is a movable contact arm ll mounted to pivot about spin ll,saidarmtendingtobeheldinaninoperative circuit breaking position by means of a go spiral spring II.

The actual contact blade 1y denoted generally by 20 is of compound character so as tobeself-cleaninginactionandsoastoavoid deleterious arcing or sparking. 'Ihis will be more a; fully described later.

Contact arm I1 is connected by a fledble conductor II with the free end of a bar or rod If, the other end of which is in turn electrically connected to terminal ll. Barf! in this embodiment 30 is substantially rigid and for adjustment of its length it is threaded at the end connected to terminal, I and is adapted for longitudinal displacement by means of adjusting nut ll and lock nut 24 co-operating with a lug II on terminal it. 35

The operating knob or handle I! is rotatably mounted on base II and carries within cover ll acrankarmllpivotallyconnectedtoslinkl'l to form a toggle mechanism. Toggle link 21 constantly tends to assume its collapsed position be- 40 cause of a spring QLJhile-a stop 2. is provided tolimittheupwardmovementofcrankarmfl above its dead centre. Toggle link I! is at its free end formed as a detentjprovtded witha shoulder adapted to 45 'contactwithswltch'arm ll. 'I'hesaidend oflink 11 passesthrough'aslot 8| formed inarm I! so astolocatesaidlinkinitsproperpositionrelatively to the switch arm II and its shoulder ll abuts aglainstacross-bar fldisposedtransvsrselyso ofslota l'romtheabovedescrlptionitwillbeclearthat rotation of operating handlei! willextend the toggle mechanism formed by crank arm II and link "and that shoulder of'saidllnkwillgg move contact arm |1 about its pivot N to cause contact between the contact blade assembly 20 and contact l5. Under normal operating conditions contact arm I1 is held in its contact making position by said toggle mechanism 26, 21 with the detent end of link 21 disposed adjacent a trigger elementi33, which is mounted on base III, to pivot about apm 34. The trigger 33 is maintained in its adjacent position by the rod 22 which is hingedly connected to said trigger at a point intermediate the pivot 34 and the operative edge 35 of the trigger.

In the embodiment-shown in Figs. 1, 4, 5 and 6 the rod 22 forms an electro-thermal overload control device in conjunction with trigger 33. Rod 22 is for this purpose made of a metal or alloy having a suitable specific electrical resistance for ex-' ample, nickel or alloys thereof, such as nickelchrome or nickel manganese and is adapted by its known expansion due to the load current carried thereby to determine the position of trigger element 33. i v

In Fig. 1 the rod 22 connected directly to trigger 33 acts when heated so as to expand in an upward direction and due to mechanical and frictional resistance of the toggle components, said rod will be in compression when displacing trigger 33 around its pivot 34 against said resistance. As

the rod will be at relatively high temperature in the case of overload it might tend to bend slightly and, therefore, it may be advisable in practice to utilize the modification shown in Fig. 2, which increases the sensitivity of the control and is particularly adapted for overload controls operative by small overload currents wherein the'diameter of the bar or wire 22 is relatively small. In Fig. 2, trigger 33 is stressed by a torsional spring 36 which tends to rotate tri ger 33 about its pivot 34 in a counter-clockwise direction. To this end spring 36 wound around pivot 34 abuts with one end against a stationary pin 31 and with the other against the underside of the operative edge 35 of trigger33. The rod 22, hingedly connected to trigger 33 as in the construction of Fig. 1, limits the pivotal movement of the trigger element and is thus in slight tension. A stop 80 is provided to limit the movement of the spring 36" after actuation of trigger 33 in order to relieve the rod 22 if very hot of any stress due to the action of the spring 36.

The compound contact assembly 20 of switch |1 comprises a current carrying contact 40 and an arcing extension 4|. Contact 4| is bifurcated by a slot 45 (see Fig. 12) to form an arm 42 carrying a metal contact brush 43 and anauxiliary contact brush 44. The arm 42 is bent as indicated at a, b and c to form a contact face 46 in tandem with the brush 43.

pressure due to the contact of brush 43 and extension 50 flexes the arm 42 and raises the area 46 away from theplane of the brush 44, as shown in Fig.9. Continued closing movement brings the area 46 into contactwith fixed contact l5 and subsequent movement carries the current'carrye ing brush 40 into engagement with the fixed metal contact l5, as shown in Fig. 10. Finally the completed movement of arm |1 causes the end of arm 42, carrying the brush 43 to rock about the bend a and to raise the brush 43 out of contact with the extension 50, as shown in Fig. 11, the slit 45 rendering the arm 42 sufficiently flexible to efiect clean and smooth to carry the normal load current. During normal operation with the contact arm |1 closed the brush 43 does not contact the carbon or other extension 50, thus avoiding all risk of abnormal rise in temperature due to faulty contact and the need for careful facing of the contacts 43 and 50. The arrangement provided is thus capable of use for considerable periods without attention and has the further advantage of allowing the main current carrying brush '40 to comprise as many laminations at necessary.

The formation of the toggle link 21 at the detent end is of considerable importance if maximum sensitiveness is to be obtained. Fig. '1 shows the link 21 on an enlarged scale and beyond the shoulder 30 are formed faces 5|, 52, 53 and 54. The shoulder 30 itself is formed as an arc of a circle struck from a centre 0 located on a vertical line through the centre 0 comprising the pivotal axis of link 21 but displaced upwardly from said centre. This allows a reduction of the frictional effect of the shoulder against the crossbar 32 and thus lessens the releasing effort.

The surface 5| which is intended to bear directly against the operative edge 35 of trigger 33 when the contact arm is in its closed position is located in the horizontal plane through the centre 0. The face 54 is inclined for the purpose of allowing displacement of the link 21 upwardly when the link is being moved during extension of the toggle according to the normal path of movement of the detent end of the link without, however, contacting with the operative edge 35 of the trigger 33 during normal load to an extent sufiicient to release shoulder 30 from crossbar 32.

The face 53 is formed so that it passes over the operative edge 35 of the trigger without affecting the relative positions of the cross-bar 32 and shoulder 30. For this purpose the face 52 is bevelled off to prevent cooperation between link 21 and the operative edge 35 at this stage.

During the closing movement of the contact arm l1, face 54 first contacts with edge 35, more or less, according to the length of rod 22 occasioned by the load and its original adjustment as shown in Fig. 4. Then the surface 35 travels across the edge 53 of the trigger without disturbing the relative positions of the cross-bar 32 and the shoulder 30, as shown in Fig. 5, while the axis of the crank arm 26 is in alignment with the axis of link 21 and edge 35. Continued movement of crank arm 26 then forces the face 5| into contact with the edge 35 as shown in Fig. 6 so that in the final set position face 5| bears against the edge 35 with the cross-bar 32 and shoulder 36 in sensitive engagement.

In operation the circuit breaker is moved to the closed or set position by rotating handle H to the "on" position, thus spreading the toggle 20, II and causing the shoulder to engage the crossbar 32. This displaces the contact arm l1 and brings the contact 43 into engagement with the extension Iii, with the subsequent movements of the auxiliary arm 44 and the contact area 4, as previously described, until the current carrying brush 40 contacts with the fixed contact I! and the contact brush it moves out of contact with the extension III. At this moment the circuit is established and the toggle is held extended.- During this movement the faces of the detent end of link 21 have taken part in their responsive movements already described with the cross-bar 32 engaging that part of shoulder 80 according to the desired overload-time factor.

If an overload occurs throughany cause trigger it is raised in consequence of the expansion of rod 22 and its operative edge It raises the link 21 until shoulder It is disengaged from cross-bar 32 when the contact arm is released and is moved to the right by the action of spring ll, thus breaking the circuit in the successive movement shown in Figs. 11, 10, 9, and 8, respectively. If the over load is comparatively small and persists for only a short period of time, the trigger edge 35 will not lift the link 21 sufliciently far to disenga shoulder 30 from cross-bar 32 owing to the time taken for the rod 22 to expand and operate the trigger, since the releasing action is dependent on the multiple function of the value of the overload and the duration thereof and can be adjusted by the setting of the adjusting nuts 23 and 24.

The device of the invention has been described in connection with single pole circuit breakers but obviously the invention can be applied to breakers having two or more poles by mere multiplication of the devices already described in connection with a single pole circuit breaker.

When the circuit breaker is of the single pole type it is immaterial whether the contact l1 and trigger 33 are formed of insulating material with the necessary electrical connection between the contact assembly '20 and the conductor II or otherwise and it is preferred in this caseto use an all-metal construction, but when the device is provided with two or more control devices in a multipolar arrangement the said devices and their cooperating parts must obviously be electrically insulated from one another.

It is to be understood that if an attempt is made to reset the circuit breaker during the continuance of an overload, short circuit, or the like, the toggle link 21 is automatically tripped by the trigger edge 35 on the resetting movement, so that manual resetting cannot be eflected until the current reaches normal value on closing the circuit.

In order to retain the cover II in position on the base Hi, the cover is apertured so as to fit over a stud Iii mounted on the base It and having a holding nut H for securing the cover. The stud is preferably provided with a transverse channel 12 through which a wire 18 can be passed and have its ends secured by a seal ll to prevent undesired tampering.

Further, the operating handle II of the circuit breaker may be coated on one side, as at 15, with a luminous paint as shown in Figs. 13 and 14 so that the position of setting of each individual device may readily be ascertained in the dark. In the case of an inoperative circuit breaker with its circuit opened the operating handle in the of! position can be more readily observed due to the presence ofv the luminous paint which is clearly visible with the handle in that position. i

to expand longitudinally due dueto'the What I claim is:

1. An electrical circuit breaker which includes a stationary contact having a metal contact block and an extension, a movable switch arm carrying contacts adapted to eo-opera'te with said stationary contact to close the circuit and comprising a main current carrying brush co-operating with said metal contact block and an arcing brush, said latter brush being bifurcated to form an auxiliary brush and a flexible arm, a metal contact at the free end of said flexible arm adapted initially to contact said extension on closing movement of said switch arm and to flex said flexible arm and a projection intermediate the axis of said flexible arm adapted to contact said metal contact block on continued movement of said switch arm in order to rock said arm and to separate said metal contact from said extension when said main brush contacts said metal contact block, manually operable means for moving said switch arm and including a detent releasably engaging said arm, electrical overload motive device and means for transmitting movement of said overload device to said detent to cause disengagement of said detent from said arm and a consequent opening of said circuit.

2. An electrical circuit breaker which includes a stationary contact, a movable switch arm carrying at least one contact adapted to co-operate with said stationary contact to close the circuit, manually operable means for moving said switch arm and including a detent releasably engaging said arm, an electrical overload motive device comprising a rod in said electrical circuit adapted to expand longitudinally due to the heating effect of the current in said circuit and a pivoted element mounted to pivot in the direction of the longitudinal dimension of said rod in engagement with said rod and with said detent and positively actuated by the expansion of said rod responsive to an overload current to release said detent from said switch arm and to cause opening of said circuit.

3. An electrical circuit breaker which includes a stationary contact, a movable switch arm carrying at least one contact adapted to co-operate with said stationary contact to close the circuit, manually operable means for moving said switch arm and including a detent releasably engaging said arm, an electrical overload motive device comprising a rod in said electrical circuit adapted to the heating eifect of the current in said circuit, a pivoted element engaging said detent and in contact with said rod, said rod on expansion positively moving said pivoted element, spring means assisting the force of expansion of said rod to cause said pivoted element to release said detentfrom said switch arm, spring means moving said switch arm on said release into a position separating said contacts and means to relieve the tension of said first mentioned spring from said pivoted element immediately after release of said detent.

4. An electrical circuit breaker, which includes a stationary contact, a movable switch arm carrying at least one contact adapted to cooperate with said stationary contact to close the circuit. manually operable means for moving said switch arm into and out of its circuit closing position, and means to release automatically said switch arm from its circuit closing position in responseto an I electrical overload,

including an electrical-over load motive device comprising a rod in saidelec- 'taiexpand longitudinally effectofthe current in said tricalcircuit circuit and arranged so that said expansion! comprising toggle mechanism including a crank and a detent pivotally connected to said crank and releasably engaging said am and means to release automatically said detent from said switcharm in response to an electrical overload, including an electrical overload motive device comprising a rod in said electrical circuit adapted to expand longitudinally due to the heating efiect of the current in said circuit and arranged so that said expansion responsive to overload current provides a positive actuating force for releasing said switch arm, said rod at the moment of release acting as a strut member and means to provide unconstrained expansion of said rod subsequent to said release.

6. An electrical circuit breaker, which includes a stationary contact, a movable switch arm carrying at least one contact adapted to cooperate with arm, comprising toggle mechanism including a crank and a link formed as a detent pivotally connectedvto said crank and releasabiy engaging said arm at a pointremote from its connection to said crank, a pivoted element engaging said detent at a point'on the side of its point of engagement with saidarm remote from its connection to said crank, an overload motive device comprising a rod in said electrical circuit, said rod being adapted to expand longitudinally due to the heating effect of the current in said circuit and being connected at one end to said pivoted element and having its other end fixed, the expansion of said rod in response to a predetermined overload providing a positive actuating force for moving said pivoted element sumcient to disengage said detent from said arm, means to provide unconstrained expan- UMBERT A. comm. 

